usinesses around Boston remembered colleagues killed in the Sept. 11 terrorist attacks yesterday, striving to strike a balance between mourning those lost and the resolve to keep working.

''These people were unwitting soldiers in a new kind of war, and you can't make complete sense of out it,'' Raytheon Co. chief executive Daniel Burnham said after an early afternoon ceremony at its Lexington headquarters, where a wreath was laid in honor of four Raytheon victims of the terrorist strikes, Peter Gay, Stan Hall, Dave Kovalcin, and Ken Waldie.

''But each of us needs to work through our own feelings about what happened a year ago, and what's happened since then,'' Burnham said. ''We can't just simply move forward.''

At the Waltham Internet software company Netegrity, more than 200 local employees and family members gathered for an hourlong memorial service for James Hayden, the company's chief financial officer who died on United Flight 175. Their computers displayed screen-saver images with Hayden's portrait and an American flag.

The Rev. Mark T. Cregan - president of Stonehill College, a Catholic priest, and a close friend of Hayden's widow Gail - and business motivational speaker Richard Whiteley, who is also a spiritual healer in the Shamanist tradition, spoke about Hayden's legacy.

Company chief executive Barry Bycoff - who was scheduled to be on the flight with Hayden, but was two minutes late because of traffic and delays getting through security - ''talked about his struggle of trying to understand why Jim and not him,'' said Jill Maunder, Netegrity's vice president of human resources. ''It was very moving. It was a very diverse kind of service.''

Boston-area retailers and firms were among thousands across the country that took steps to remember victims, such as opening late, lowering flags to half staff, and observing moments of silence to honor the victims. Many companies took out spare, patriotic-themed ads in local newspapers to mark the anniversary of the attacks.

In New York, the stock exchanges made time for a morning of tributes at the New York Stock Exchange. A General Motors assembly line in Linden, N.J., shut down for a half-hour to toll a bell to remember six relatives of workers who died in the attacks. Sears, Roebuck and Co. took a one-day moratorium on calling delinquent credit card holders.

On Wall Street, stocks drifted downward in light trading during a shortened session after the New York Stock Exchange remained closed until noon and the Nasdaq stock market did not begin trading until 11 a.m. Both normally open at 9:30 a.m. After small rallies early, the Dow Jones industrial average and Nasdaq both fell by less than 0.5 percent, with the Dow down 21.44 points, at 8,581.17, and the Nasdaq off 4.64 points, to 1,315.45.

The nation's airlines, anticipating much lighter travel, sharply reduced their flight schedule. With tight flight restrictions over airspace in New York and Washington and a beefed-up presence of federal air marshals, US air traffic dropped about 30 percent from last week's levels, according to the Federal Aviation Administration. US Airways said it cut 100 flights, and advance bookings were only about 35 percent of capacity.

Amerian Airlines and United Airlines, whose planes were used in the Sept. 11 attacks, distributed commemorative ribbons to flight crews, and pilots asked passengers on hundreds of flights to observe moments of silence.

Internet companies marked Sept. 11, as well, from a patriotic ribbon at the Google search engine to Yahoo replacing its usual splashy home-page graphics with a somber gray backdrop and a black ''We remember'' tribute box.

AOL Time Warner replaced banner ads at its sites with images of candles and links to Web sites where surfers could make donations to agencies caring for families of Sept. 11 victims or volunteer for service organizations.

The tributes at Boston-area companies for lost colleagues were highly private affairs that ranged from memorial services to calls for silent reflection.

At the PricewaterhouseCoopers office in Boston's Financial District, employees marked five minutes of silence at noon to remember five colleagues, four of them from Boston, who died in the crashes of the hijacked jets.

That gesture followed a tribute this summer that saw employees donate 1,100 hours of community service to organizations such as the Greater Boston Food Bank and Pine Street Inn in honor of Kelly Booms, Brian Kinney, Jessica Sachs, and Patrick J. Quigley.

''When you're sitting still, reflecting, five minutes does seem like an awfully long time,'' said Michael Costello, the accounting firm's Boston managing partner. ''Just about everybody in our office had a friend, a family member, a classmate who was connected to everything that happened in New York.''

Akamai Technologies, the Cambridge Internet company whose 31-year-old cofounder Daniel Lewin died when Los Angeles-bound American Airlines Flight 11 became the first hijacked jet to slam into a World Trade Center tower, held a private service but also remembered Lewin with a tribute at its Web page.

''Akamai lost a friend, colleague, and visionary, Danny Lewin,'' the tribute read. ''Although a year has passed, Danny's spirit and energy remains strong in all of us at Akamai. His vision continues to guide us as we carry on his commitment to Akamai's success.''

Needham's Alta Communications, a 25-person Web video technology company, closed for the day in memory of partner David Retik, 33, and analyst Chris Mello, who died in American Flight 11.

The TJX Cos. - the Framingham operator of such retail chains as T.J. Maxx, Marshalls, HomeGoods, and A.J. Wright - lost seven employees on Sept. 11. On the first anniversary of the terrorist attacks, its US stores opened at noon, local time, after a moment of silence.

Earlier this month, in separate ceremonies for their family members and for employees, TJX dedicated a memorial garden at its headquarters to its lost associates: Christine Barbuto, Neilie Heffernan Casey, Tara Kathleen Creamer, Linda George, Lisa Fenn Gordenstein, Robin Kaplan, and Susan Mackay.

Among other Sept. 11 victims from Greater Boston's business community who were remembered yesterday were Anna Williams Allison of Stoneham, president of A2 Software Solutions; Peter P. Hashem of Tewksbury, an employee of Teradyne Inc.; Judith Frankel Laroque of Framingham, founder and chief executive of high-tech research firm Market Perspectives Inc.; Richard Ross, 58, principal of management consulting firm The Ross Group in Boston; and Sun Microsystems software designer Philip Rosenzweig of Acton.

In a telephone interview after the private ceremony at Raytheon, Burnham said he has thought hard about ''what's really important, God, country, and family, and I think I've become more conscious of those over the past year.